This invention relates to a system for performing an assay of a biological cell sample, and more particularly, for providing an automated method and arrangement of measuring attributes of the cells of the sample and classifying sampled cells in accordance with the measured attributes.
The diagnosis/prognosis of a possible cancer typically includes the removal of a cell sample, such as a tissue mass, from the patient. Although an attending physician may have good intuition regarding the patient's diagnosis/prognosis, confirmation of the diagnosis with a histological examination of the cell sample removed from the patient is necessary. The histological examination entails cell staining procedures which allow the morphological features of the cells to be seen relatively easily in a light microscope. A pathologist, after having examined the stained cell sample, makes a qualitative determination of the state of the tissue and reaches a conclusion regarding the prognosis for the patient. While this diagnostic method has a long history, it is somewhat lacking in scientific rigor since it is heavily reliant on the subjective judgment of the pathologist and it is extremely time consuming.
The optical evaluation of cell samples, and particularly those taken from tissue sections, is a difficult procedure. The optical field presented to an evaluator is a disordered collection of cell objects, some on top of one another and others being only fragments of whole cell objects. The optical field shows only boundaries of two-dimensional optical entities filled with varying levels of contrast. Some of the overlapped cell objects appear to be large and/or dense single cell objects and some of the cell object fragments appear to have sufficient size to be whole cell objects. Faced with this random cluster of images, the evaluator's difficult and time-consuming task is the selection of single whole cell objects which can accurately represent the cell sample and the classification of those selected objects into categories which classification aids in the final diagnosis/prognosis.
It is well known that the DNA content of cell objects can provide valuable information in cancer diagnosis. Systems have been developed which utilize the DNA content of cell objects to improve histological examination. In U.S. Pat. No. 4,471,043 to Bacus for Method and Apparatus for Image Analyses of Biological Specimens, an automated method and a system for measuring the DNA of cells are disclosed which employ differential staining of the DNA in cell nuclei with a Feulgen stain and image processing. After staining, optical fields of the cell sample are presented to an evaluator who selects objects for analysis and categorizes the selected objects. Certain attributes including the DNA mass of the operator selected cell objects are then measured and used to produce reports such as DNA histograms.
The arrangement and method of Bacus U.S. Pat. No. 4,471,043 have been well received both for the reports generated and for the improvements in the use of operator time. The operator, however, must still select relevant cell objects from the optical field presented and classify the selected cell objects into classes before machine measurement of attributes occurs. Such selection and classification requires the thoughtful review of each object in the random cluster of images of an observed field. Further, the only input information available for such review is the varying contrast levels presented by the visual image. When the operator must evaluate cell samples for a long period of time, as is the case in some pathology laboratories, concentration by the operator and accuracy of the decisions made, may be affected.
A need exists for an automated method and arrangement for use with a DNA analysis apparatus, which selects whole, single cell objects and classifies each selected cell object as being in a particular one of a plurality of diagnostic aiding categories as well as in particular regions of the DNA distribution. The automatic selection and classification of cell objects speeds analysis and reduces the tedium of the operator. Also, pre-selection and classification by the apparatus permits the operator to concentrate his or her efforts on the difficult and subtle analysis of the preselected cell objects which are likely to be representative of the sample.
The evaluation of cell objects and their accurate reporting is at its most difficult when a sample is taken from a tissue section. The act of slicing the tissue section also slices and distorts some of the cell objects which are to be observed and analyzed. The viewed field of a tissue section sample contains many small cell object fragments which have almost no analysis value, but must be evaluated by the observer. Other fragments are substantial parts of cell objects, which due to size or optical density, will be selected and reported as whole cell objects. When reports such as DNA histograms are prepared, a selected fragment consisting of 75% of a whole cell object will be counted as a whole cell object having approximately 75% of the DNA contained by the original (pre-sliced) cell object. Thus, the histogram will include a cell object having smaller DNA mass value than should have been reported. Greater report accuracy can be achieved when the cell object attributes such as DNA mass of fractional cell objects can be corrected to represent whole cell objects before those attributes are used in preparing the final reports.
A need exists for evaluation methods and apparatus which identify cell object fragments likely to possess analysis value and properly correct their measured attributes to reflect what those attributes would have been, had the identified cell object not been fragmented.